RESUMO
Acinetobacter guillouiae SFC 500-1A, a native bacterial strain isolated from tannery sediments, is able to simultaneously remove high concentrations of Cr(VI) and phenol. In this complementary study, high-resolution microscopy techniques, such as atomic force microscopy (AFM) and transmission electron microscopy (TEM), were used to improve our understanding of some bacterial adaptive mechanisms that enhance their ability to survive. AFM contributed in gaining insight into changes in bacterial size and morphology. It allowed the unambiguous identification of pollutant-induced cellular disturbances and the visualization of bacterial cells with depth sensitivity. TEM analysis revealed that Cr(VI) produced changes mainly at the intracellular level, whereas phenol produced alterations at the membrane level. This strain tended to form more extensive biofilms after phenol treatment, which was consistent with microscopy images and the production of exopolysaccharides (EPSs). In addition, other exopolymeric substances (DNA, proteins) significantly increased under Cr(VI) and phenol treatment. These exopolymers are important for biofilm formation playing a key role in bacterial aggregate stability, being especially useful for bioremediation of environmental pollutants. This study yields the first direct evidences of a range of different changes in A. guillouiae SFC 500-1A which seems to be adaptive strategies to survive in stressful conditions.
Assuntos
Acinetobacter , Adaptação Biológica/efeitos dos fármacos , Cromo/toxicidade , Viabilidade Microbiana/efeitos dos fármacos , Fenol/toxicidade , Poluentes Químicos da Água/toxicidade , Acinetobacter/efeitos dos fármacos , Acinetobacter/ultraestrutura , Biodegradação Ambiental , Biofilmes/crescimento & desenvolvimento , Microscopia de Força Atômica , Microscopia Eletrônica de TransmissãoRESUMO
An L-amino acid oxidase (LAAO) from Crotalus durissus cumanensis venom (CdcLAAO) was purified to homogeneity using a combination of size-exclusion and ion exchange chromatographies. CdcLAAO is a monomeric protein exhibiting an apparent molecular mass of 55 kDa and a calculated pI of 8. Its complete 498-amino-acid sequence was deduced through cDNA and protein sequencing. The enzyme oxidized L-Leu with K(m) and a V(Max) of 9.23 µM and 0.46 µM/min respectively, and exhibited Kcat and a Kcat/K(m) of 1.8 s(-1) and 195 mM(-1)s(-1). CdcLAAO inhibited in a dose-dependent manner the growth of Staphylococcus aureus and Acinetobacter baumannii. The inhibitory effect was more significant on S. aureus, with a Minimal Inhibitory Concentration (MIC) of 8 µg/mL and Minimal Bactericidal Concentration (MBC) of 16 µg/mL, than against A. baumannii, with a MIC of 16 µg/mL and MBC of 32 µg/mL. However, against Escherichia coli CdcLAAO did not show inhibitory capacity at the concentrations tested (2-128 µg/mL). CdcLAAO did not exhibit cytotoxic activity on the mouse myoblast cell line C(2)C(12) and on peripheral blood mononuclear cell (PBMC).
Assuntos
Acinetobacter/efeitos dos fármacos , Antibacterianos/farmacologia , Venenos de Crotalídeos/enzimologia , Crotalus/metabolismo , L-Aminoácido Oxidase/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Acinetobacter/crescimento & desenvolvimento , Acinetobacter/ultraestrutura , Sequência de Aminoácidos , Animais , Antibacterianos/química , Antibacterianos/isolamento & purificação , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Cromatografia por Troca Iônica , Clonagem Molecular , Venenos de Crotalídeos/genética , DNA Complementar/metabolismo , Humanos , L-Aminoácido Oxidase/química , L-Aminoácido Oxidase/genética , L-Aminoácido Oxidase/isolamento & purificação , Leucócitos Mononucleares/efeitos dos fármacos , Camundongos , Testes de Sensibilidade Microbiana , Dados de Sequência Molecular , Mioblastos/efeitos dos fármacos , Oxirredução , Estrutura Terciária de Proteína , Análise de Sequência de DNA , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Staphylococcus aureus/crescimento & desenvolvimento , Staphylococcus aureus/ultraestruturaRESUMO
Acinetobacter baumannii ha emergido en los últimos años como una etiología importante de infecciones intrahospitalarias (IIH). De los 19 biotipos que conforman la especie, los biotipos 9 y 8 constituyen aproximadamente el 90 por ciento de las cepas aisladas en nuestro país, desconociéndose los factores que favorecen su mayor prevalencia. En el presente estudio hemos investigado mediante microscopía electrónica, la presencia de cápsula en dos cepas de A. baumannii, biotipos 9 y 8 aislados de IIH durante 1995 en el Hospital San Juan de Dios. Cultivos por la noche en agar sangre fueron teñidos con azul de Alsacia y tratados con antisueros específicos. Se estudió igualmente las características de hidrofobicidad de las bacterias y la presencia de cápsula al microscopio de luz. Se observó al microscopio electrónico una capa densa de material capsular en ambas cepas. Las cepas se caracterizaron asimismo por ser hidrofílicas y presentar un halo compatible con una cápsula al microscopio de luz. Es probable que la cápsula otorgue a estos microorganismos una superficie hidrofílica y contribuya a su mayor virulencia y prevalencia en los hospitales chilenos
Assuntos
Humanos , Infecções por Acinetobacter/diagnóstico , Infecção Hospitalar/diagnóstico , Microscopia Eletrônica , Acinetobacter/classificação , Acinetobacter/isolamento & purificação , Acinetobacter/ultraestrutura , Hospitais Públicos , Infecção Hospitalar/etiologia , Infecção Hospitalar/microbiologiaRESUMO
BACKGROUND: Acinetobacter baumannii is an important nosocomial pathogen whose virulence factors have not been fully elucidated. AIM: To study the adherence and hemagglutinating capacity of several biotypes of Acinetobacter baumannii. MATERIAL AND METHODS: Thirty nine strains of Acinetobacter baumannii isolated from hospitalized patients were studied. The adherence of these strains to small pieces of rat tracheal tissue was studied. Additionally, their ability to hemagglutinate human erythrocytes and the effect of D-mannose and D-galactose on the adherence and hemagglutinating capacity was assessed. Transmission electron microscopy of strains was performed looking for the presence of fimbriae. RESULTS: All strains exhibited adherence to tissues. All strains had also D-mannose and D-galactose resistant hemagglutinating ability. Fimbriae were found in Acinetobacter baumannii and E coil cells. CONCLUSIONS: Adherence of Acinetobacter baumannii to rat tracheal tissue, apparently not related to the presence of fimbriae, may be a virulence mechanism of this bacterium.
Assuntos
Acinetobacter/patogenicidade , Aderência Bacteriana , Traqueia/microbiologia , Acinetobacter/classificação , Acinetobacter/isolamento & purificação , Acinetobacter/ultraestrutura , Infecções por Acinetobacter/microbiologia , Animais , Técnicas de Tipagem Bacteriana , Escherichia coli/ultraestrutura , Ratos , Ratos Sprague-DawleyRESUMO
Acinetobacter baumannii, an important nosocomial pathogen is usually found on various surfaces in the hospital environment. In this work, the ability to form biofilms on the surface of sterile coverslips by one clinical isolate of A. baumannii was studied. Sessile cells which adhered to coverslips after being immersed in a nutrient-deficient mineral medium were observed by epifluorescence and scanning electron microscopy at various times of incubation. A rapid increase in the number of sessile cells in young biofilms, followed by a slower increase of such cells was found. At 48 h biofilms were clearly visible and an amorphous material similar to the exopolysaccharide described in some other bacteria covered sessile cells was evident. Biofilm formation by A. baumannii probably favours its maintenance on solid surfaces in the hospital environment and protects the micro-organism against some antibacterial factors.
Assuntos
Acinetobacter/fisiologia , Biofilmes/crescimento & desenvolvimento , Acinetobacter/ultraestruturaRESUMO
Caffeine and related xanthines were identified as potent stimulators for the bacterial cellulose production in A. xylinum. These compounds are present in several plants whose infusions are useful as culture-medium supplements for this acetobacterium. The proposed target for these native purine-like inhibitory substances is the novel diguanyl nucleotide phosphodiesterase(s) that participate(s) in the bacterial cellulogenic complex. A better understanding of this feature of A. xylinum physiology may facilitate the preparation of bacterial cellulose pellicles, which are applied as a biotechnological tool in the treatment of skin burns and other dermal injuries.